Conventionally, a flash unit (illumination unit) is proposed, which is retracted with respect to the camera body when not used, and is protruded from the camera body only when used. In a camera having such a flash unit, the flash unit is biased toward the protrusion position by a biasing member such as a spring. Further, a lock mechanism is provided, which holds the flash unit at the retraction position against the biasing force of the biasing member when not used, and releases the holding to move the flash unit to the protrusion position (see Japanese Patent Laid-open application No. H07-56225).
The lock mechanism holds the flash unit at the retraction position by the engagement of the flash unit and a hook member biased by a biasing member. The engagement of the flash unit and the hook member is released by rotating the hook member against the biasing force of the biasing member when the flash unit is moved from the retraction position to the protrusion position.
Here, there is a possibility that a gap is generated between the flash unit and the camera body depending on the relationship between the force of the biasing member for biasing the flash unit toward the protrusion position and the force of the biasing member for biasing the hook member holding the flash unit at the retraction position.
In addition, in the mechanism including the above-mentioned hook member, a certain degree of gap for inserting an engaging portion of the flash unit, which engages with the hook member, is required between the hook member and the camera body that are in a nonengagement state.
However, generating the gap between the flash unit and the camera body makes it easier for dusts to enter the camera body through the gap and deteriorates the external appearance quality of the camera.
For solving the problem, a camera having a gap adjustment mechanism for adjusting the gap between the flash unit and the camera body is proposed in Japanese Patent Laid-open application No. H07-56226.
However, providing the gap adjustment mechanism, proposed in Japanese Patent Laid-open application No. H07-56226, to the camera increases the number of parts, and thereby resulting in increases of the assembly processes, costs and the size of the camera.
On the other hand, there is a structure for reducing the gap size, in which the flash unit is held by a strong force at the retraction position by making the force for biasing the hook member stronger.
However, in this structure, a strong force is required for releasing the engagement of the hook member and the flash unit. Therefore, in a case where an actuator is used for driving the hook member, for example, the driving power of the actuator must be larger.
Further, in this case, there is a possibility that the frictional force between the engaging portion of the flash unit and the hook member increases, and the abrasion of them by the frictional force is generated. Thereby, it becomes difficult to move the flash unit smoothly between the retraction position and the protrusion position.